Mass spectrometers are devices that ionize a sample and then determine the mass-to-charge ratios of the collection of ions formed. One well-known mass spectrometer is the Time-Of-Flight Mass Spectrometer (TOFMS), in which the mass-to-charge ratio of an ion is determined by the amount of time required for that ion to be transmitted under the influence of electric fields from the ion source to a detector. The spectral quality in the TOFMS reflects the initial conditions of the ion beam prior to acceleration into a field free drift region. Specifically, any factor that results in ions of the same mass having different kinetic energies and/or being accelerated from different points in space may result in a degradation of spectral resolution and, thereby, a loss of mass accuracy.
Matrix-Assisted Laser Desorption Ionization (MALDI) is a well-known method to produce gas-phase biomolecular ions for mass spectrometric analysis. The development of Delayed Extraction (DE) for MALDI-TOF has made high-resolution analysis routine for MALDI-based instruments. In DE-MALDI, a short delay is added between the ionization event, triggered by the laser, and the application of the accelerating pulse to the TOF source region. The fast (i.e., high-energy) ions will travel farther than the slow ions, thereby transforming the energy distribution upon ionization to a spatial distribution upon acceleration (in the ionization region prior to the extraction pulse application).
See U.S. Pat. Nos. 5,625,184, 5,627,369, 5,760,393, and 9,536,726. See also, Wiley et al., Time-of-flight mass spectrometer with improved resolution, Review of Scientific Instruments vol. 26, no. 12, pp. 1150-1157 (2004); M. L. Vestal, Modern MALDI time-of-flight mass spectrometry, Journal of Mass Spectrometry, vol. 44, no. 3, pp. 303-317 (2009); Vestal et al., Resolution and mass accuracy in matrix-assisted laser desorption ionization-time-of-flight, Journal of the American Society for Mass Spectrometry, vol. 9, no. 9, pp. 892-911 (1998); and Vestal et al., High Performance MALDI-TOF mass spectrometry for proteomics, International Journal of Mass Spectrometry, vol. 268, no. 2, pp. 83-92 (2007). The contents of these documents are hereby incorporated by reference as if recited in full herein.